Time-Resolved Studies of the Spin-Transfer Reversal Mechanism in Perpendicularly Magnetized Magnetic Tunnel Junctions

TL;DR

This study investigates the time-resolved spin-transfer switching mechanisms in perpendicularly magnetized magnetic tunnel junctions, revealing size-dependent stochastic and deterministic switching behaviors influenced by pulse amplitude.

Contribution

It provides new insights into the size and pulse amplitude dependence of switching dynamics and identifies long-lived intermediate states affecting switching rates.

Findings

Switching time inversely depends on pulse amplitude.

Switching onset is stochastic in 50 nm junctions but fast once initiated.

Larger junctions show pulse amplitude-dependent switching times, with long-lived intermediate states.

Abstract

Pulsed spin-torque switching has been studied using single-shot time-resolved electrical measurements in perpendicularly magnetized magnetic tunnel junctions as a function of pulse amplitude and junction size in 50 to 100 nm diameter circular junctions. The mean switching time depends inversely on pulse amplitude for all junctions studied. However, the switching dynamics is found to be strongly dependent on junction size and pulse amplitude. In 50 nm diameter junctions the switching onset is stochastic but the switching once started, is fast; after being initiated it takes less than 2 ns to switch. In larger diameter junctions the time needed for complete switching is strongly dependent on the pulse amplitude, reaching times less than 2 ns at large pulse amplitudes. Anomalies in the switching rate versus pulse amplitude are shown to be associated with the long lived (> 2 ns) intermediate junction resistance states.